This project is concerned with the permeability of the pulmonary barriers which separate the airspaces and blood in both animals and man. Studies will be continued of a new procedure which permits measurements of the rate radioactive indicators diffuse through these membranes in man. Radionuclides (principally 99mTc-DTPA, diethylenetriaminepentaacetate) are inhale in aerosol droplets and the subsequent regional disappearance of radioactivity is monitored with a scintillation camera. The clearance of these indicators is accelerated in many patients with a variety of chronic lung disorders (e.g., Hamman-Rich syndrome, pneumoconioses and sarcoid), among smokers (in whom it rapidly returns to normal after abstinence) and in patients with pulmonary edema due to lung injury (ARDS). We plan to continue studies which suggest that ARDS can be distinguished from pulmonary edema due to congestive heart failure with this approach. In addition, the incidence of abnormal scans will be determined in patients with asbestosis. Animal models will be used to evaluate (1) active (?) transport of 99mTcO4- and other ions in the lungs, (2) clearance following instillation or aerosolization of indicator, (3) differences between large and small airway clearance, and (4) passage of small nonpolar membranes across cell membranes in the exchange area of the lungs. A new procedure will be used to measure pleural and pulmonary parenchymal permeability to extracellular indicators.